The present invention relates to a method for assembling an actuator head suspension assembly that forms part of a magnetic disk device, an optical magnetic disk device, or the like. More particular, the invention relates to a technique for preventing the head suspension assembly from being damaged by electrostatic discharge.
The actuator head suspension assembly used in the magnetic disk device includes an actuator assembly and a head suspension assembly. The head suspension assembly includes a load beam, a hinge, a mount plate, a flexure assembly, and the like. The flexure assembly includes a head/slider including a head and a slider, a flexure for supporting the head/slider, and a lead connected to the head.
The head suspension assembly is mounted on the actuator assembly. Performing a pivotal motion as driven by a voice coil motor, the head suspension assembly can bring the head to a desired track on a magnetic disk surface. The head/slider flies above the magnetic disk surface with an extremely small clearance therefrom by balancing an upward lift received from an air flow of the magnetic disk surface against a pressing load applied thereto by the load beam. The head/slider thereby performs a gimbal motion to follow the track.
Requirements for control characteristics and read/write performance of the head have become even more stringent to respond to the increased data recording density of the magnetic disk in recent years. The current situation is that effects of weight, layout, and the like of leads on the head suspension assembly on head positioning control can no longer be ignored. As a result, a trend now is toward adopting a flexure assembly incorporating integrated wires (hereinafter referred to as an “integrated wire flexure assembly”). The integrated wire flexure assembly reduces variations in gimbal characteristics of the flexure as caused by a wire, which may be bonded to the flexure or a pattern of which may be formed in the flexure. Another trend is toward incorporating a GMR read head that makes use of “giant magnetoresistive” (GMR) effect that allows a sufficiently powerful read output to be obtained even from a feeble magnetic field.
In the integrated wire flexure assembly, a lead connected to the head is constructed as follows. Specifically, the lead is a laminated structure including a metal layer, a first dielectric layer, a conductor layer, and a second dielectric layer. The metal layer and the conductor layer sandwich the first dielectric layer therebetween to form a capacitor structure. The head suspension assembly goes through a cleaning process before being supplied to an assembly process of the actuator head suspension assembly. Static electricity is generated from the cleaning process using ultrapure water and through contact, friction, or the like among different parts in the assembly process of the head suspension assembly. The capacitor structure thereby accumulates an electric charge.
In the assembly process of the actuator head suspension assembly, a soldered connection is made between the lead of the integrated wire flexure assembly and a terminal of a flexible printed circuit board (hereinafter referred to as an “FPC”) of the actuator assembly. An FPC lead may be grounded directly or through a resistor. As soon as the soldered connection is made, therefore, the electric charge accumulated in the capacitor structure of the head suspension assembly is quickly discharged, causing a large current to flow through the head. Even if the FPC lead itself is not grounded, a large current could flow the moment an external terminal for connecting the FPC lead to a circuit board of the magnetic disk device contacts a metallic part. The GMR read head that is extremely sensitive, in particular, is highly likely to be damaged by the discharge of even a small amount of static electricity.
If the head is damaged in the assembly process of the actuator head suspension assembly, it becomes necessary to re-manufacture the entire flexure assembly. This could lead to a delay in fabricating processes and an increase in material costs. Static electricity has conventionally been neutralized by installing an ionizer in assembly environment for the actuator head suspension assembly or placing the head suspension assembly on a ground panel.
Japanese Patent Laid-open No. 2000-21157 discloses a static electricity protective device for a read/write head. The protective device provides protection when the read/write head is transported or assembled into a magnetic disk device. During such a time as recited above, the protective device reliably maintains a short-circuited state for a terminal of a read/write element to protect the read/write element from a discharge of an electric charge. The protective device also allows the short-circuit to be easily removed when the read/write head is to be assembled into the magnetic disk device or connected to an external circuit.